SIMULATION OF WATER-WAVES GENERATED BY A POTENTIAL DEBRIS AVALANCHE IN MONTSERRAT, LESSER-ANTILLES

The evolution of the volcano activity in Montserrat could lead to the collapse of a portion of the lava dome in the Tar River Valley and to a sudden entry of debris avalanche into the Caribbean Sea. The impact of a debris avalanche with a volume of 40x10(6) m(3) into the sea and the generated tsunami have been simulated numerically by a mixture mod el solving the 3D Euler's equations. The mixture is composed of sedime nts considered as an homogeneous fluid of density 2 and of water. Nume rical tests show that the generated waves are sensitive to both initia l impact velocities and avalanche fronts of the landslide. The water s urface and velocities calculated by the 3D mixture model are used as i nput data in a non-linear shallow water model, to calculate tsunami pr opagation along the coasts of Montserrat. The hydraulic risks in Monts errat are roughly assessed for a tsunami generated by a mass of 40x10( 6) m(3) entering the sea.